1. Technical Field
The present invention relates to an image reading device which reads an image of an original by projecting light to the original.
2. Description of Related Art
There are facsimile machines provided with an image reading device which reads an image of an original by projecting light to the original while transporting it and detecting the reflected light. FIG. 2 is a cross-sectional view of an image reading device and an original eject portion of a conventional facsimile machine.
In the image reading device as shown in FIG. 2, an original guide member 21 forms a flat guide surface 21A leading from an image sensor 19 to an original eject slot 20, with an upper edge 20A of the slot 20 positioned above the guide surface 21A.
The image reading device has the following problem. External light such as sunlight or electric light is reflected by a desk surface or the like, and the reflected light enters the interior of a casing of the facsimile machine through the original eject slot 20 to be directly incident on a reading surface of the image sensor 19. This results in reduced image reading quality. To solve the problem, there has been an attempt to attach a plastic film to a casing for covering an original eject slot. However, this construction may cause further problems: increased production costs involved by increased component parts, and lowered original ejecting performance.
There has been thus proposed an image reading device in which an original guide surface formed by an original guide member leading from an image sensor to an original eject slot, and the original eject slot, are positioned differently from those in the foregoing conventional image reading device, as described in Japan Laid-open Patent Publication No. H10-200673.
FIG. 3 is an enlarged view of a relevant part of the image reading device as disclosed in Japanese Laid-open Patent Publication No. 10-200673. In the image reading device, as illustrated in FIG. 3, an original guide member 27 for guiding an original is provided with a step portion 24 between an image sensor 22 and an original eject slot 26. More specifically, the original guide member 27 is formed by a first guide surface 25 and a second guide surface 23 which is raised by the height of the step portion 24. The height of the step portion 24 is set such that an upper edge 26A of the original eject slot 26 is positioned below an extended plane 23A of the second guide surface 23.
The Publication argues that this arrangement prevents the incidence of the external light on a reading surface of the image sensor 22 without involving increased component parts and lowered original ejecting performance.
In the image reading device, however, there is a certain distance between the original eject slot 26 and the image sensor 22, and incoming external light is reflected there. Consequently, lowering of image reading quality of the image sensor 22 caused by the incident external light cannot be resolved sufficiently. It is possible to prevent the reflection and refraction by blackening the original guide member 27. If the original guide member 27 is exposed to the exterior, however, design restrictions make it difficult to change only the color of the original guide member 27 arbitrarily.
Moreover, the image reading device has a large opening of the original eject slot 26 and a wide space above the image sensor 22 and the original guide member 27. Thus, the incoming light through the original eject slot 26 is reflected by inner members of the device, causing the lowering of image reading quality of the image sensor 22.